Pressure fluid container



Aug 8, 1967 O. J. VAN LEER ETAL 3,334,780

PRESSURE FLUID CONTAINER Filed dot. 26. 1964 2 Shees-Sheet l we m f. www 0 n m/f 4 M Ww/Mw M i f ff a Aug 8, 1967v o. J. VAN LEER ETAI. 3,334,780

PRESSURE FLUID CONTAINER Filed Oct. 26, 1964 2 Sheets-Sheet 2 ,WMM/QM United States Patent O ce 3,334,780 PRESSURE FLUID CGNTAINER Oscar J. van Leer, Kortenhoef, Netherlands, and Christian Ragettii, Zurich, Switzerland, assignors to Metal Containers Limited, London, England, a company of the United Kingdom Filed Oct. 26, 1964, Ser. No. 406,533 Claims priority, application Great Britain, Oct. 24, 1963, 41,992/ 63 Claims. (Cl. 22d-89) The present invention relates generally to containers and, more particularly, to containers of the type used for packaging, storing, transporting and distributing pressure uid such as liquefied petroleum gas. In its principal aspeet, the invention is concerned with improved pressure uid containers which, because of their construction, are substantially free of any tendency to explode vwhen subjected to excessively high ambient temperature conditions such as may be encountered when, for example, a re occurs in the building or other structure within or near which such containers are located.

Various types of containers have heretofore been used for storing pressure tluids--uids which may be, for example, a liquefied petroleum gas such as butane or propane. In some instances the containers have been formed of sheet Imetal such, merely by way of example, as steel. In other instances, the containers have been formed of nonmetallic materials, such as in the case Where the container has one or more filament wound shells consisting of, for example, glass filaments impregnated with an epoxy or similar synthetic resin, the latter being cured in any suitable manner either subsequent to or during formation of the shell or shells, It will, of course, be appreciated that since such containers are intended to package, store, transport, or distribute a fluid medium, it is essential that the containers, including the Walls thereof, be fluidtight or fluid-impervious, and this is true irrespective of the particular material or materials used in forming such containers. Stated another way, if such containers were not fluidtight or Huid-impervious, they would be unsuitable for their intended use since the fiuid contents of the containers would be either lost due to leakage or contaminated by foreign substances which penetrate into the containers, or both.

Unfortunately, however, the very fact that such containers are, and must be, Huid-impervious has introduced a serious handling problem for -users thereof. This is due to the fact that, heretofore, when a conventional pressure fiuid container has been subjected to excessively high temperature conditions, as, for example, when a re has occurred in the immediate vicinity, increased ambient temperatures have resulted in excessive pressure rise within the container, thereby significantly increasing the risk yof explosion. Indeed, such factors have often led to actual explosions with attendant losses not only of the containers and their contents, but also of personnel, equipment, and fixtures in the immediate area.

Accordingly, it is a general aim of the present invention to provide improved container constructions which overcome the foregoing disadvantage, yet which, under normal conditions, retain the advantageous and essential characteristic of fluid-imperviousness, thereby permitting effective use of such containers in the handling of both combustible and noncombustible pressure fiuids, While at the same time minimizing the risk of explosions and the hazards attendant such explosions. While not so limited in its application, the invention will find especially advantageous use in connection with liquefied petroleum gas containers of the type having one or more filament wound shells.

A related object of the invention is the provision of 3,334,780 Patented Aug. 8, 1967 improved pressure fluid container constructions which preclude build-up of excessive internal pressures within the containers resulting from either unintentional or deliberate increases in ambient temperatures, thereby eliminating or, at the very least, significantly reducing, the danger of explosion. v

A more specific object of the invention is the provision of a pressure Huid container which, although Huid-impervious at normal temperature conditions, becomes fluidpervious upon subjection to ambient temperatures above a known critical level, thereby permitting controlled escape of the fluid contents of the container and thus control of and limiting of pressure -rise within the container.

In another of its important aspects, it is an object of the invention to provide improved means for rendering a normally duid-impervious container pervious upon exceeding a predetermined critical temperature and which may be readily incorporated with pressure vessels of the same general type as are commonly used in the industry, thus permitting formation of containers embodying the invention by means of known fabricating techniques and equipment. In this connection, it is an object of the invention to provide an improved container of the foregoing character suitable for use in storing pressure uids and which permits of economical fabrication from a wide variety of commercially available materials.

Other objects and advantages of the invention will become apparent as the following description proceeds, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a side elevation of an exemplary container embodying the features of the invention, such container here being depicted in partial vertical section so as to expose the interior portions of the container; and

FIG. 2 is a view similar to FIG. 1 of a slightly modified container construction also embodying features of the present invention.

While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as expressed in the appended claims.

Referring now to the drawings, there is illustrated in FIG. 1 an exemplary container, generally indicated at 10 which, while particularly suitable for storing a liquefied petroleum gas such as butane or propane, is also suitable for use in storing a Wide range of other pressure fluids. As the ensuing description proceeds, it will become apparent that the particular material or materials used in forming the Wall or walls of the container 10 is not critical to the present invention. For example, it will be understood that the container walls could be formed of metallic or nonmetallic materials, as well as from a wide range of other natural or synthetic materials. Indeed, the particular material used in any given situation will depend upon a number of factors such as the cost of the container, availability of raw materials, permissible weight of the container, the nature of the material to be stored therein, and other similar consideratitons. In each instance, however, it is essential that the container 10 be uidimpervious under normal conditions so as to insure that the uid contents of the container are neither lost nor contaminated.

However, in order to facilitate an understanding of one environment in which the invention finds particularly advantageous applicability, the exemplary container 10 is here shown as a double-walled or multi-ply filament wound vessel having inner and outer shells 11 and 12, respectively, each shell consisting of suitably wound iilaments impregnated with a resin that is cured in any suitable manner either subsequent to or during formation of the shell. In the illustrative construction, an internally threaded annular fitting 14 is rigidly affixed to the container for the purpose of receiving a conventional closure and discharge valve (not shown) or the like. To this end, the fitting 14 is provided with a generally radial ange 15 which is in engagement with the inner surface of the inner shell 11, the fitting projecting axially outward through the shells 11 and 12 and being fixed in place by means of a flanged retaining ring 16. As here shown, the marginal edge of the inner shell 11 is clamped between the ange 15 and the anged retaining ring 16, with the outer shell 12 being wound about the flange 18 formed on the ring 16. Thus, the arrangement is such that the inner and outer shells 11 and 12 respectively, the fitting 15, and the ring 16 may all be adhesively or resinously bonded to one another so as to form a unitary construction.

It will, upon inspection of FIG. l, be observed that the lower end of the exemplary container 10 is also provided with an axially disposed flanged fitting 19 which is held in place by means of a fianged retaining ring 20. In this instance, however, the flanges 21, 22 on the fitting 19 and ring respectively are adhesively bonded to opposite sides of the marginal edge of the outer shell 12. Moreover, it will also be noted that the inner shell 11 is here formed with a relatively large polar opening 24 disposed at the lower end of the container. In the exemplary construction, the annular open space defined by that portion of the opening 24 between the inner shell 11 and the fiange 21 is here closed by a portion 25 of the outer shell 12, such portion 25 being formed by winding the outer shell 12 through the open space incident to formation thereof, thus closing the opening 24.

While filament wound vessels may be made with a wide variety of different types of winding equipment and by various well known conventional winding techniques, a container of the foregoing type and its method of manufacture are more fully described in the copending application of Christian Ragettli and Ian Leeuwerik, Ser. No. 418,235, filed Dec. 16, 1964 and assigned to the assignee of the present invention. Those interested in a more detailed description of the specific structural details of such containers or in the method of manufacture thereof are referred to the aforesaid Ragettli et al. application.

It should suffice, however, for the purpose of understanding the present invention, to point out that in conventional container constructions, the wall of the filament wound vessel (here defined by the |shells 11 and 12) is preferably fluid impervious, thus inhibiting leakage of uids either into or out of the container. This may be accomplished in various ways. For example, the vessel wall may consist of at least one wound shell having a wall or shell thickness sufficiently great to insure that the superimposed filament layers therein effectively close the interstices between filaments, thus producing a nonporous shell. Alternatively, the shell may be impregnated, exteriorly coated, or interiorly lined with a fiuid impermeable substance. Merely by way of example, those skilled in the art will appreciate that the exemplary container 10 could be rendered fluid impervious by lining or coating either or both of the inner and vouter shells 11 and 12 with a layer of butyl rubber or the like.

'In accordance with one of the important aspects of the present invention, there is provided a container 10 which, although fiuid impervious at normal ambient temperatures, becomes fluid pervious at a predetermined elevated temperature level so as to permit controlled escape of at least a portionof the fluid contents of the container, thus preventing excessive pressure rise within the container and thereby preclucling, or at least inhibiting, explosions resulting from increased ambient temperatures. To this end, the exemplary container 10 is provided with a fluid impervious wall which in this instance comprises the inner wound shell 11, such shell being leakproof throughout except in the region of the large polar opening 24.

As indicated above, formation of a nonporous shell can be accomplished in various ways such, forexample, as by impregnating, externally coating, or internally lining the shell 11 with a uid impervious substance. Alternatively, this may be accomplished by winding filaments about a mandrel (not shown), such filaments being either moistened or impregnated with a suitable binder such as epoxy resin reither before, during or after the winding operation, so as to form a shell 11 having a sufi'icient thickness to insure that all interstices between filaments are closed by subsequent filament laye-rs. After a shell 11 of predetermined thickness is formed, the resin is cured (e.g., by heat treatment or by chemical action, both of which are procedures well known to those skilled in the art), and the mandrel is then removed through the large polar opening 24. Thus, it will be noted that a fluid impervious inner shell having the desired opening 24 is created incident to formation of the shell, it being understood that the desired characteristic of fluid impermeability can be achieved either by controlling shell thickness or byV applying a fluid impervious substance thereto.

In carrying out the invention, provision is made for closing the polar opening 24 lformed in the Viiuid impervious inner shell 11 by means of a lporous or uid pervious material. Again, while this can be accomplished in various ways, it is advantageously done incident to formation of the vessel by winding the outer shell 12 about the inner shell 11 with the outer shell including a portion 25 which bridges the open space formed in the vessel 10 by the polar opening 24. However, in this instance, the thickness of the shell 12, or at least the portion 25 thereof, is contr-olled so as to insure that the interstices between filaments are not closed by subsequent filament layers, thus producing an outer shell 12 which envelops the inner shell 11 and which is porous, at least in the region 25. Alternatively, the shell 12 may tbe porous throughout, it being understood that the inner shell 11 is fluid impervious throughout.

In order to insure that the fluid contents of the container do not escape through the polar opening 24 and the porous portion 25 of the outer shell 12 under normal conditions, and in keeping with the principal objectives of the invention, provision is made for closing or sealing the multiplicity of fluid escape paths extending through the opening 24 and the interstices in the porous portion of the outer shell 12 by means of Ia material which is normally fluid impervious, but which characteristically changes its properties when subjected to ambient temperatures in excess of a known critical level. In the exemplary form of the invention, this is accomplished by sealing the polar opening 24 and the porous region 25 of the outer shell 12 by means of a closure member 26 or bottom cake formed of a desired material which is fiuid impervious at normal temperatures, thus normally preventing discharge or leakage of the fluid contents from the container 10.

It will be understood that the particular material selected for the normally fluid impervious `closure member 26 is not critical to the present invention provided that such material becomes fluid pervious in response to heat above a predetermined critical level. Thus, the closure member can be formed of a material which, although solid and fiuid impervious at normal ambient temperatures, cracks, shrinks, becomes particulate, creeps, flows plastically, foams, melts or liquefies, or otherwise disintegrates when subjected to heat. However, the particular material selected must be characterized by being decomposable at elevated temperatures or by its capability to undergo some change in property at such temperatures whereby the uid contents of the container can escape through the opening 24 inthe inner shell 11 and the interstices in the porous outer shell 12. Consequently, the term disintegrate is used herein and in the appended claims to generically connote a material which, although fluid impervious at normal temperature conditions, undergoes a change in state when heated and thus becomes leaky or fluid pervious.

As a consequence of the foregoing construction, a container made in accordance with the invention will provide a leakproof chamber for the particular uid being stored therein at normal temperature conditions. However, when heated above a known critical level, the material of the closure member 26 undergoes a change in state, thus becoming uid pervious and permitting the liuid contents of the container to escape through the polar opening 24 and the interstices between filaments in the outer shell 12. Since the outer shell 12, or at least the portion 25 thereof,

is porous, the uid does not suddenly escape in great quantities but, to the contrary, it seeps or leaks out of the container in a plurality of small jets which are discharged through the pores of the shell 12. Indeed, where the entire outer shell 12 is porous, the area of jet-like discharge may be somewhat greater than the area of the opening 24 in the shell 11. Thus, the arrangement is such that excessive pressure rise within the container 10 is prevented and, even where the escaping uid is combustible, the net result may simply be that the various escaping jets will be ignited and burn.

Having in mind the foregoing structural details and the requisite general characteristics of the closure member 26, it will be appreciated that the latter could be formed of a widerange of materials, one or more of which vn'll be selected by the manufacturer or user because of specific prevalent conditions or requirements. Thus, a particular material may be selected because of its availability or cost, or because of its compatibility with the fluid to be stored in the container. In some instances, the permissible weight of the material and thus the container will be a factor which enters into the ultimate decision. Merely by way of example, however, it has been found that excellent results are achieved Where the closure member 26 comprises or Iconsists of a synthetic organic resin such as a thermosetting resin including -a reactive exibilizer. For example, the member 26 may include or may be based on an epoxy resin employing a suitable hardener such as an amine hardener (e.g., diethylene triamine) or an anhydride hardener (e.g., polymeric anhydride or trimellitic anhydride hardeners). Polysullide may be used as a exibilizer. Those skilled in the art will, of course, recognize that epoxy resin technology is well established and, therefore, it should not be necessary to specify in detail the various techniques relating thereto. Those interested in more complete understanding of epoxy technology are referred to Epoxy Resins by Kirk and Othmer, Encyclopedia of Chemical Technology, iirst supplement volume, page 312, published by Interscience. However, to make clear one illustrative type of material that can be used, it is noted that very satisfactory results have been obtained by using a mixture comprising 1700 parts of flexible epoxy resin, 100 parts of polysuliide flexibilizer, and l0 parts of amine hardener.

Preferably, a exible epoxy resin is used in the formation of the closure member 26 having an epoxy equivalent of from 215 to 800. The amine hardener used preferably has an amine equivalent on the order of 50.

In those instances where a thermosetting material is used in the manufacture of the closure member 26, such material may, if desired, be or include a polyester based on isophthalic acid, or adipic acid, or a mixture of such polyesters, while making use of methylethylketon peroxide as a catalyzer and a polysulfide as a flexibilizer.

Referring to FIG. 2, there is illustrated a slightly modiiied container construction 10A which is somewhat similar in construction and mode of operation to the exemplary container 10 shown in FIG. l, the modified container 10A also embodying the invention. In this instance, however, the container 10A includes a liuid impervious inner shell 28 having a relatively large polar opening 24 disposed at its upper end ycoaxial with a relatively small diameter ange fitting 29 suitable for reception of a closure and discharge valve or the like (not shown). A s here shown, the fitting includes la generally radially extending ange 30 (which may or may not be spider-like in configuration) and which is in engagement with and preferably bonded to, the outer surface of the inner shell 28 adjacent the marginal shell edge defining the opening 24.

As with the exemplary container construction 10 (FIG. 1), the outer shell, indicated at 31 in FIG. 2, is wound about the inner shell 28 in such a manner as to overlie the flange 30 on the tting 29, thus assisting in fixing the latter to the inner shell 28. Moreover, in this instance the outer shell 31 is also porous in construction, at least in the area overlying and proximate to the ange 30, thus insuring that a plurality of escape paths are formed in the container 10A extending Vthrough the opening 24 and the adjacent porous portion of the outer shell 31. If desired, the container 10A may also include a bottom fitting 32 which is held in place by means of a suitable retaining ring 34, the ring 34 and tting 32 serving to clamp the adjacent marginal edge 3S of at least one of the Wound shells, here the edge of the inner shell 28. Again, the opening 24 in the inner shell 28 and the desired porosity of at least a portion of the outer shell 31 may be readily established incident to winding the container 10A in the manner previously described and as set forth in greater detail in the aforesaid copending application of Christian Ragettli and I an Leeuwerik.

In carrying out the modified form of the invention, the iiuid escape paths through the opening 24 and the porous portion of the outer shell 31 are normally sealed by means of a heat-disintegratable closure member which is formed of a material that undergoes a change in physical or chemical characteristics, or both, incident to an increase of ambient temperature above a known critical level. To this end, an upper closure member 36 or top cake is secured to the upper tting .29 by means of a mounting ring 38. Thus, the arrangement is such that when the ambient temperature exceeds a known critical value, for example, when 4a re occurs, the Imaterial of the closure member 36 will creep, crack, shrink, ow plastically, foam, melt, liquify, or otherwise disintegrate, thus becoming leaky and permitting the uid contents of the container to pass through the opening 24, around the ange 30, and into the space between the inner and outer shells 28, 31 from where the iiuid is discharged through the pores or interstices between filaments in the porous portions of the outer shell 31. Consequently, excessive internal pressure rise is precluded -as the gaseous or uid contents of the container 10A are discharged through all or a portion of the porous outer shell 31 in a plurality of small jets.

It will be apparent to those skilled in the art that the Amaterial from which the top cake 36 is made could be similar or identical to the illustrative thermosetting materials heretofore described. Moreover, it will also be understood that the closure members 26, 36 could, if desired, be formed of materials other than thermosetting materials of the type described above. Por example, such closure members could comprise or consist of a destructible or fusible metal plug adapted to melt when subjected to high ambient temperatures. Such a member could, for example, be formed of Woods Metal, lead, or other suitable low melting point elemental metals or metallic alloys. Thus, when melted, the molten material could simply drop away from the opening 24 thereby exposing the porous outer shell (as in the construction shown in FIG. 2) or, alternatively, the molten material might itself escape through the porous outer shell, exposing the latter to the uid container contents as, for example, in the construction shown in FIG. l.

It will, of course, be understood from the foregoing that the opening 24 in the fluid impervious inner shell can be located virtually anywhere therein and, consequently, the porous closure for the opening (e.g., the porous outer shell) and the disintegratable closure (e.g.,

Vthe closures 26 or 36) could also be similarly located anywhere about the container. However, since -a polar opening 24 may be conveniently formed in the inner shell 11, 28 incident to winding thereof, the novel temperature responsive'fluid escape mechanism of the invention is also advantageously disposed at one of the polar ends of the container. Preferably, the temperature responsive fiuid escape mechanism is vlocated at or adjacent the upper end of the container as best shown in FIG. 2, thereby insuring that any relatively cool liquid in the container does not tend to cool the disintegratable closure and thus retard disintegration of the latter. Consequently, the safety valve action provided by the olosure member 36 is not impeded by the contents of the container.

The predetermined critical temperature level at which the closure members 26, 36 disintegrate or become leaky may, of course, vary dependent upon the chraracteristics of the fluid contents of the container. Preferably, however, the closure members 26, 36 will be formed of a material which undergoes a change in either or both physical and chemical characteristics at ambient temperatures in excess of one hundred degrees centigrade (100 C.). Thus, if the container is to be used for holding propane, the closure members 26, 36 will preferably disintegrate at approximately one hundred and thirty degrees centigrade (130 C.); while if the container is used to hold butane, the critical temperature level may be on the order of one hundred and sixty degrees centigrade (160 C.). Merely by way of example and not by way of limitation, when a given container is to be used in storing propane, the closure members 26, 36 could be formed of an alloy consisting of approximately forty percent (40%) lead and sixty percent (60%) bismuth, such an alloy having a melting temperature on the order of 130 C. Similarly, if the container is intended for use in holding butane, the closure members 26, 36 could be formed of an alloy consisting of approximately thirty percent (30%) lead and seventy percent (70%) bismuth, anV alloy which has a melting point in the vicinity of 160 C.

It will be appreciated from the foregoing that there has herein been described various container constructions which, although fluid impervious under normal operating conditions, become fluid pervious at and above critical ambient temperature levels, thereby substantially eliminating the risk of explosion due to increased pressure within the container. Obviously, however, various modifcations could be made without departing from the spirit and scope of the invention as expressed in the appended claims. For example, as described herein, the outer shell could be porous throughout or, alternatively, only in a localized area overlying an opening formed in the iiuid impervious inner shell. Moreover, whi-le the disintegratable closure members 26, 36 are here shown as plug-like in configuration and adapted to be applied internally of the inner shell, it will be understood that such elements could comprise internal linings or external coatings applied to either or both of the inner and outer shells. Thus, it is required only that the disintegratable closure be so arranged and applied that it entirely seals off (at normal temperatures) any uid escape paths extending through the shells. In addition, while the containers 10 and 10A are here shown as double-walled, they could include only a single shell, in which event the shell would be fluid impervious throughout a major portion of its surface and fluid pervious throughout a relatively small portion of its surface, with the disintegratable closure sealing the porous portion. And, of course, the disintegratable closure member need not be disintegratable throughout, but can include only a portion which changes characteristics when subjected to heat, provided that such change unseals the porous portion of the container so as to allow leakage or escape of the container contents.

It has been found in practice that the use of the present invention in conjunction with double-walled shells presents additional advantagesA quite apart from the explosionproof features of the invention. This is due to the fact that in the event a container is dropped or otherwise subjected to deformation forces, there is a tendency for the inner and outer shells to separate and, since the outer shell is porous, air is therefore slowly admitted between the shells so as to produce a shock absorbing eect. However, in carrying out the present invention in accordance with its preferred forms, at least the annular peripheral edges of the closure members 26, 36 are formed of a flexible material which acts as a dilatation joint between the edge of the inner shell (shell 11 in FIG. 1 and 28 in FIG. 2) surrounding the opening 24 and the adjacent annular portion of the outer porous shell 12, 31 (FIGS. 1 and V2 should a container beV dropped, for example, thus resulting in relative movement' respectively). Consequently,

between, and perhaps spacing of, the inner and outer shells adjacent the polar opening 24, the relatively exible closure member (member 26 in FIG. l and 36K in FIG. 2) will serve to prevent the formation of lea-ks.

As used herein and in the appended claims, the term metal is intended to embrace either elemental metals or metallic alloys which have a relatively low melting point. Similarly, the phrase low'meltiug point as used in conjunction with metallic materials is intended to connote a material which disintegrates or melts at a predetermined temperature level which is below the temperature at which excessive temperature induced pressure rises are created within the container which tend to make the latter explode. Y

We claim as our invention:

1. A container for pressure fluids such as liquefied petroleum gas or the like comprising, in combination, a fluid impervious first shell having an opening extending therethrough, a second shell at least partially enveloping said first shell, said second shell including a portion overlying said opening in said first shell with at least said portion of said second shell being porous, said opening and said porous portion of said second shell defining a multiplicity of liuid escape paths, and heat responsive disintegratable sealing means sealing said paths for normally preventing escape of the fluid contents of said container, said sealing means being adapted to undergo a change in property incident to increase of ambient temperature above a predetermined critical level whereupon said sealing means becomes leaky and said fluid escape paths are opened to permit controlled discharge of atV least a portion of the contents of said container.

2. A container for pressure fluids such as liquefied petroleum gas or the like comprising, in combination, a fluid impervious shell for receiving such fluids, said shell being filament wound and having an opening formed therein and extending therethrough, porous fluid pervious means closing said opening, and heat responsive disintegratable means normally sealing said opening whereupon increase of ambient temperatures above a predetermined level will cause said heat responsive disintegratable means to change its properties and become leaky so as to permit controlled escape of at least a part of the fluid contents of said container through said porous iiuid pervious means.

3. A container as set forth in claim 2 further characterized in that said porous uid perviousV means comprises filament windings defining interstices extending therethrough.

4. A container as set forth in claim 3 further characterized in that said porous fluid pervious means comprises a second filament wound shell at least partially enveloping said first named shell.

5. A container as set forth in claim 3 further characterized in that said -filament windings define a portion of said filament wound shell.

6. A container for pressure fluids such as liquefied petroleum gas or the like comprising, in combination, a

fluid impervious shell for receiving such fluids, said shell having an opening formed therein and extending therethrough, porous liuid pervious means closing said opening, a fitting extending through said opening and said porous uid pervious means, and heat responsive disintegratable means normally sealing said opening whereupon increase of ambient temperatures above a predetermined level will cause said heat responsive disintegratable means to change its properties and become leaky so as to permit controlled escape of at least a part of the fluid contents of said container through said porous fluid pervious means.

7. A container for pressure fluids such as liquefied petroleum gas or the like comprising, in combination, a iiuid impervious rst shell having an opening extending therethrough, a second shell at least partially enveloping said rst shell, said second shell including a portion overlying said opening in said first shell with at least said portion of said second shell being porous, said opening and said porous portion of said second shell deiining a multiplicity of uid escape paths, and exible heat responsive disintegratable sealing means sealing said paths for normally l preventing escape of the uid contents of said container,

said flexible sealing means defining a dilatation joint between the edge of said -first shell surrounding said opening and the adjacent portion of said second shell, said sealing means being adapted to undergo a change in property incident to increase of ambient temperature above a predetermined critical level whereupon said sealing means becomes leaky and said iiuid escape paths are opened to permit controlled discharge of at least a portion of the contents of said container.

8. A container for pressure iluids as set forth in claim 1 further characterized in that said second shell is entirely porous.

9. A container for pressure fluids as set forth in claim 1 further characterized in that at least one of said rst and second shells consists of filament windings.

10. A container for pressure iluids as set forth in claim 1 further characterized in that said rst and second shells consist of iilament windings.

References Cited UNITED STATES PATENTS 822,826 6/1906 Coleman 220-89 900,763 10/ 1908 McNutt 220-89 1,219,493 3/1917 Scott 220-89 2,271,786 2/ 1942 Watkins 220-89 3,132,761 5/1964 Sylvester 2201-3 3,245,578v 4/1966i Sutton 220-89 THERON E. CONDON, Primary Examiner. RAPHAEL H. SCHWARTZ, Assistant Examiner. 

1. A CONTAINER FOR PRESSURE FLUIDS SUCH AS LIQUEFIED PETROLEUM GAS OR THE LIKE COMPRISING, IN COMBINATION, A FLUID IMPERVIOUS FIRST SHELL HAVING AN OPENING EXTENDING THERETHROUGH, A SECOND SHELL AT LEAST PARTIALLY ENVELOPING SAID FIRST SHELL, SAID SECOND SHELL INCLUDING A PORTION OVERLYING SAID OPENING IN SAID FIRST SHELL WITH AT LEAST SAID PORTION OF SAID SECOND SHELL BEING POROUS, SAID OPENING AND SAID POROUS PORTION OF SAID SECOND SHELL DEFINING A MULTIPLICITY OF FLUID ESCAPE PATHS, AND HEAT RESPONSIVE DISINTEGRATABLE SEALING MEANS SEALING SAID PATHS FOR NORMALLY PREVENTING ESCAPE OF THE FLUID CONTENTS OF SAID CONTAINER, SAID SEALING MEANS BEING ADAPTED TO UNDERGO A CHANGE IN PROPERTY INCIDENT TO INCREASE OF AMBIENT TEMPERATURE ABOVE A PREDETERMINED CRITICAL LEVEL WHEREUPON SAID SEALING MEANS BECOMES LEAKY AND SAID FLUID ESCAPE PATHS ARE OPENED TO PERMIT CONTROLLED DISCHARGE OF AT LEAST A PORTION OF THE CONTENTS OF SAID CONTAINER. 